/*
 * Copyright 2002-2019 the original author or authors.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      https://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package org.springframework.util;

import org.springframework.lang.Nullable;

import java.lang.reflect.Constructor;
import java.lang.reflect.Field;
import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;
import java.lang.reflect.Modifier;
import java.lang.reflect.UndeclaredThrowableException;
import java.sql.SQLException;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.List;
import java.util.Map;

/**
 * Simple utility class for working with the reflection API and handling
 * reflection exceptions.
 *
 * <p>Only intended for internal use.
 *
 * @author Juergen Hoeller
 * @author Rob Harrop
 * @author Rod Johnson
 * @author Costin Leau
 * @author Sam Brannen
 * @author Chris Beams
 * @since 1.2.2
 */
public abstract class ReflectionUtils
{

    /**
     * Pre-built MethodFilter that matches all non-bridge methods.
     *
     * @since 3.0
     * @deprecated as of 5.0.11, in favor of a custom {@link MethodFilter}
     */
    @Deprecated
    public static final MethodFilter NON_BRIDGED_METHODS = (method -> !method.isBridge());

    /**
     * Pre-built MethodFilter that matches all non-bridge non-synthetic methods
     * which are not declared on {@code java.lang.Object}.
     *
     * @since 3.0.5
     */
    public static final MethodFilter USER_DECLARED_METHODS = (method -> !method.isBridge() && !method.isSynthetic() && method.getDeclaringClass() != Object.class);

    /**
     * Pre-built FieldFilter that matches all non-static, non-final fields.
     */
    public static final FieldFilter COPYABLE_FIELDS = (field -> !(Modifier.isStatic(field.getModifiers()) || Modifier.isFinal(field.getModifiers())));


    /**
     * Naming prefix for CGLIB-renamed methods.
     *
     * @see #isCglibRenamedMethod
     */
    private static final String CGLIB_RENAMED_METHOD_PREFIX = "CGLIB$";

    private static final Method[] EMPTY_METHOD_ARRAY = new Method[0];

    private static final Field[] EMPTY_FIELD_ARRAY = new Field[0];


    /**
     * Cache for {@link Class#getDeclaredMethods()} plus equivalent default methods
     * from Java 8 based interfaces, allowing for fast iteration.
     */
    private static final Map<Class<?>, Method[]> declaredMethodsCache = new ConcurrentReferenceHashMap<>(256);

    /**
     * Cache for {@link Class#getDeclaredFields()}, allowing for fast iteration.
     */
    private static final Map<Class<?>, Field[]> declaredFieldsCache = new ConcurrentReferenceHashMap<>(256);


    // Exception handling

    /**
     * Handle the given reflection exception. Should only be called if no
     * checked exception is expected to be thrown by the target method.
     * <p>Throws the underlying RuntimeException or Error in case of an
     * InvocationTargetException with such a root cause. Throws an
     * IllegalStateException with an appropriate message or
     * UndeclaredThrowableException otherwise.
     *
     * @param ex the reflection exception to handle
     */
    public static void handleReflectionException(Exception ex)
    {
        if (ex instanceof NoSuchMethodException)
        {
            throw new IllegalStateException("Method not found: " + ex.getMessage());
        }
        if (ex instanceof IllegalAccessException)
        {
            throw new IllegalStateException("Could not access method: " + ex.getMessage());
        }
        if (ex instanceof InvocationTargetException)
        {
            handleInvocationTargetException((InvocationTargetException) ex);
        }
        if (ex instanceof RuntimeException)
        {
            throw (RuntimeException) ex;
        }
        throw new UndeclaredThrowableException(ex);
    }

    /**
     * Handle the given invocation target exception. Should only be called if no
     * checked exception is expected to be thrown by the target method.
     * <p>Throws the underlying RuntimeException or Error in case of such a root
     * cause. Throws an UndeclaredThrowableException otherwise.
     *
     * @param ex the invocation target exception to handle
     */
    public static void handleInvocationTargetException(InvocationTargetException ex)
    {
        rethrowRuntimeException(ex.getTargetException());
    }

    /**
     * Rethrow the given {@link Throwable exception}, which is presumably the
     * <em>target exception</em> of an {@link InvocationTargetException}.
     * Should only be called if no checked exception is expected to be thrown
     * by the target method.
     * <p>Rethrows the underlying exception cast to a {@link RuntimeException} or
     * {@link Error} if appropriate; otherwise, throws an
     * {@link UndeclaredThrowableException}.
     *
     * @param ex the exception to rethrow
     * @throws RuntimeException the rethrown exception
     */
    public static void rethrowRuntimeException(Throwable ex)
    {
        if (ex instanceof RuntimeException)
        {
            throw (RuntimeException) ex;
        }
        if (ex instanceof Error)
        {
            throw (Error) ex;
        }
        throw new UndeclaredThrowableException(ex);
    }

    /**
     * Rethrow the given {@link Throwable exception}, which is presumably the
     * <em>target exception</em> of an {@link InvocationTargetException}.
     * Should only be called if no checked exception is expected to be thrown
     * by the target method.
     * <p>Rethrows the underlying exception cast to an {@link Exception} or
     * {@link Error} if appropriate; otherwise, throws an
     * {@link UndeclaredThrowableException}.
     *
     * @param ex the exception to rethrow
     * @throws Exception the rethrown exception (in case of a checked exception)
     */
    public static void rethrowException(Throwable ex) throws Exception
    {
        if (ex instanceof Exception)
        {
            throw (Exception) ex;
        }
        if (ex instanceof Error)
        {
            throw (Error) ex;
        }
        throw new UndeclaredThrowableException(ex);
    }


    // Constructor handling

    /**
     * Obtain an accessible constructor for the given class and parameters.
     *
     * @param clazz          the clazz to check
     * @param parameterTypes the parameter types of the desired constructor
     * @return the constructor reference
     * @throws NoSuchMethodException if no such constructor exists
     * @since 5.0
     */
    public static <T> Constructor<T> accessibleConstructor(Class<T> clazz, Class<?>... parameterTypes) throws NoSuchMethodException
    {

        Constructor<T> ctor = clazz.getDeclaredConstructor(parameterTypes);
        makeAccessible(ctor);
        return ctor;
    }

    /**
     * Make the given constructor accessible, explicitly setting it accessible
     * if necessary. The {@code setAccessible(true)} method is only called
     * when actually necessary, to avoid unnecessary conflicts with a JVM
     * SecurityManager (if active).
     *
     * @param ctor the constructor to make accessible
     * @see java.lang.reflect.Constructor#setAccessible
     */
    @SuppressWarnings("deprecation")  // on JDK 9
    public static void makeAccessible(Constructor<?> ctor)
    {
        if ((!Modifier.isPublic(ctor.getModifiers()) || !Modifier.isPublic(ctor.getDeclaringClass().getModifiers())) && !ctor.isAccessible())
        {
            ctor.setAccessible(true);
        }
    }


    // Method handling

    /**
     * Attempt to find a {@link Method} on the supplied class with the supplied name
     * and no parameters. Searches all superclasses up to {@code Object}.
     * <p>Returns {@code null} if no {@link Method} can be found.
     *
     * @param clazz the class to introspect
     * @param name  the name of the method
     * @return the Method object, or {@code null} if none found
     */
    @Nullable
    public static Method findMethod(Class<?> clazz, String name)
    {
        return findMethod(clazz, name, new Class<?>[0]);
    }

    /**
     * Attempt to find a {@link Method} on the supplied class with the supplied name
     * and parameter types. Searches all superclasses up to {@code Object}.
     * <p>Returns {@code null} if no {@link Method} can be found.
     *
     * @param clazz      the class to introspect
     * @param name       the name of the method
     * @param paramTypes the parameter types of the method
     *                   (may be {@code null} to indicate any signature)
     * @return the Method object, or {@code null} if none found
     */
    @Nullable
    public static Method findMethod(Class<?> clazz, String name, @Nullable Class<?>... paramTypes)
    {
        Assert.notNull(clazz, "Class must not be null");
        Assert.notNull(name, "Method name must not be null");
        Class<?> searchType = clazz;
        while (searchType != null)
        {
            Method[] methods = (searchType.isInterface() ? searchType.getMethods() : getDeclaredMethods(searchType));
            for (Method method : methods)
            {
                if (name.equals(method.getName()) && (paramTypes == null || Arrays.equals(paramTypes, method.getParameterTypes())))
                {
                    return method;
                }
            }
            searchType = searchType.getSuperclass();
        }
        return null;
    }

    /**
     * Invoke the specified {@link Method} against the supplied target object with no arguments.
     * The target object can be {@code null} when invoking a static {@link Method}.
     * <p>Thrown exceptions are handled via a call to {@link #handleReflectionException}.
     *
     * @param method the method to invoke
     * @param target the target object to invoke the method on
     * @return the invocation result, if any
     * @see #invokeMethod(java.lang.reflect.Method, Object, Object[])
     */
    @Nullable
    public static Object invokeMethod(Method method, @Nullable Object target)
    {
        return invokeMethod(method, target, new Object[0]);
    }

    /**
     * Invoke the specified {@link Method} against the supplied target object with the
     * supplied arguments. The target object can be {@code null} when invoking a
     * static {@link Method}.
     * <p>Thrown exceptions are handled via a call to {@link #handleReflectionException}.
     *
     * @param method the method to invoke
     * @param target the target object to invoke the method on
     * @param args   the invocation arguments (may be {@code null})
     * @return the invocation result, if any
     */
    @Nullable
    public static Object invokeMethod(Method method, @Nullable Object target, @Nullable Object... args)
    {
        try
        {
            return method.invoke(target, args);
        }
        catch (Exception ex)
        {
            handleReflectionException(ex);
        }
        throw new IllegalStateException("Should never get here");
    }

    /**
     * Invoke the specified JDBC API {@link Method} against the supplied target
     * object with no arguments.
     *
     * @param method the method to invoke
     * @param target the target object to invoke the method on
     * @return the invocation result, if any
     * @throws SQLException the JDBC API SQLException to rethrow (if any)
     * @see #invokeJdbcMethod(java.lang.reflect.Method, Object, Object[])
     * @deprecated as of 5.0.11, in favor of custom SQLException handling
     */
    @Deprecated
    @Nullable
    public static Object invokeJdbcMethod(Method method, @Nullable Object target) throws SQLException
    {
        return invokeJdbcMethod(method, target, new Object[0]);
    }

    /**
     * Invoke the specified JDBC API {@link Method} against the supplied target
     * object with the supplied arguments.
     *
     * @param method the method to invoke
     * @param target the target object to invoke the method on
     * @param args   the invocation arguments (may be {@code null})
     * @return the invocation result, if any
     * @throws SQLException the JDBC API SQLException to rethrow (if any)
     * @see #invokeMethod(java.lang.reflect.Method, Object, Object[])
     * @deprecated as of 5.0.11, in favor of custom SQLException handling
     */
    @Deprecated
    @Nullable
    public static Object invokeJdbcMethod(Method method, @Nullable Object target, @Nullable Object... args) throws SQLException
    {
        try
        {
            return method.invoke(target, args);
        }
        catch (IllegalAccessException ex)
        {
            handleReflectionException(ex);
        }
        catch (InvocationTargetException ex)
        {
            if (ex.getTargetException() instanceof SQLException)
            {
                throw (SQLException) ex.getTargetException();
            }
            handleInvocationTargetException(ex);
        }
        throw new IllegalStateException("Should never get here");
    }

    /**
     * Determine whether the given method explicitly declares the given
     * exception or one of its superclasses, which means that an exception
     * of that type can be propagated as-is within a reflective invocation.
     *
     * @param method        the declaring method
     * @param exceptionType the exception to throw
     * @return {@code true} if the exception can be thrown as-is;
     * {@code false} if it needs to be wrapped
     */
    public static boolean declaresException(Method method, Class<?> exceptionType)
    {
        Assert.notNull(method, "Method must not be null");
        Class<?>[] declaredExceptions = method.getExceptionTypes();
        for (Class<?> declaredException : declaredExceptions)
        {
            if (declaredException.isAssignableFrom(exceptionType))
            {
                return true;
            }
        }
        return false;
    }

    /**
     * Perform the given callback operation on all matching methods of the given
     * class, as locally declared or equivalent thereof (such as default methods
     * on Java 8 based interfaces that the given class implements).
     *
     * @param clazz the class to introspect
     * @param mc    the callback to invoke for each method
     * @throws IllegalStateException if introspection fails
     * @see #doWithMethods
     * @since 4.2
     */
    public static void doWithLocalMethods(Class<?> clazz, MethodCallback mc)
    {
        Method[] methods = getDeclaredMethods(clazz);
        for (Method method : methods)
        {
            try
            {
                mc.doWith(method);
            }
            catch (IllegalAccessException ex)
            {
                throw new IllegalStateException("Not allowed to access method '" + method.getName() + "': " + ex);
            }
        }
    }

    /**
     * Perform the given callback operation on all matching methods of the given
     * class and superclasses.
     * <p>The same named method occurring on subclass and superclass will appear
     * twice, unless excluded by a {@link MethodFilter}.
     *
     * @param clazz the class to introspect
     * @param mc    the callback to invoke for each method
     * @throws IllegalStateException if introspection fails
     * @see #doWithMethods(Class, MethodCallback, MethodFilter)
     */
    public static void doWithMethods(Class<?> clazz, MethodCallback mc)
    {
        doWithMethods(clazz, mc, null);
    }

    /**
     * Perform the given callback operation on all matching methods of the given
     * class and superclasses (or given interface and super-interfaces).
     * <p>The same named method occurring on subclass and superclass will appear
     * twice, unless excluded by the specified {@link MethodFilter}.
     *
     * @param clazz the class to introspect
     * @param mc    the callback to invoke for each method
     * @param mf    the filter that determines the methods to apply the callback to
     * @throws IllegalStateException if introspection fails
     */
    public static void doWithMethods(Class<?> clazz, MethodCallback mc, @Nullable MethodFilter mf)
    {
        // Keep backing up the inheritance hierarchy.
        Method[] methods = getDeclaredMethods(clazz);
        for (Method method : methods)
        {
            if (mf != null && !mf.matches(method))
            {
                continue;
            }
            try
            {
                mc.doWith(method);
            }
            catch (IllegalAccessException ex)
            {
                throw new IllegalStateException("Not allowed to access method '" + method.getName() + "': " + ex);
            }
        }
        if (clazz.getSuperclass() != null)
        {
            doWithMethods(clazz.getSuperclass(), mc, mf);
        }
        else if (clazz.isInterface())
        {
            for (Class<?> superIfc : clazz.getInterfaces())
            {
                doWithMethods(superIfc, mc, mf);
            }
        }
    }

    /**
     * Get all declared methods on the leaf class and all superclasses.
     * Leaf class methods are included first.
     *
     * @param leafClass the class to introspect
     * @throws IllegalStateException if introspection fails
     */
    public static Method[] getAllDeclaredMethods(Class<?> leafClass)
    {
        final List<Method> methods = new ArrayList<>(32);
        doWithMethods(leafClass, methods::add);
        return methods.toArray(EMPTY_METHOD_ARRAY);
    }

    /**
     * Get the unique set of declared methods on the leaf class and all superclasses.
     * Leaf class methods are included first and while traversing the superclass hierarchy
     * any methods found with signatures matching a method already included are filtered out.
     *
     * @param leafClass the class to introspect
     * @throws IllegalStateException if introspection fails
     */
    public static Method[] getUniqueDeclaredMethods(Class<?> leafClass)
    {
        final List<Method> methods = new ArrayList<>(32);
        doWithMethods(leafClass, method -> {
            boolean knownSignature                               = false;
            Method  methodBeingOverriddenWithCovariantReturnType = null;
            for (Method existingMethod : methods)
            {
                if (method.getName().equals(existingMethod.getName()) && Arrays.equals(method.getParameterTypes(), existingMethod.getParameterTypes()))
                {
                    // Is this a covariant return type situation?
                    if (existingMethod.getReturnType() != method.getReturnType() && existingMethod.getReturnType().isAssignableFrom(method.getReturnType()))
                    {
                        methodBeingOverriddenWithCovariantReturnType = existingMethod;
                    }
                    else
                    {
                        knownSignature = true;
                    }
                    break;
                }
            }
            if (methodBeingOverriddenWithCovariantReturnType != null)
            {
                methods.remove(methodBeingOverriddenWithCovariantReturnType);
            }
            if (!knownSignature && !isCglibRenamedMethod(method))
            {
                methods.add(method);
            }
        });
        return methods.toArray(EMPTY_METHOD_ARRAY);
    }

    /**
     * This variant retrieves {@link Class#getDeclaredMethods()} from a local cache
     * in order to avoid the JVM's SecurityManager check and defensive array copying.
     * In addition, it also includes Java 8 default methods from locally implemented
     * interfaces, since those are effectively to be treated just like declared methods.
     *
     * @param clazz the class to introspect
     * @return the cached array of methods
     * @throws IllegalStateException if introspection fails
     * @see Class#getDeclaredMethods()
     */
    private static Method[] getDeclaredMethods(Class<?> clazz)
    {
        Assert.notNull(clazz, "Class must not be null");
        Method[] result = declaredMethodsCache.get(clazz);
        if (result == null)
        {
            try
            {
                Method[]     declaredMethods = clazz.getDeclaredMethods();
                List<Method> defaultMethods  = findConcreteMethodsOnInterfaces(clazz);
                if (defaultMethods != null)
                {
                    result = new Method[declaredMethods.length + defaultMethods.size()];
                    System.arraycopy(declaredMethods, 0, result, 0, declaredMethods.length);
                    int index = declaredMethods.length;
                    for (Method defaultMethod : defaultMethods)
                    {
                        result[index] = defaultMethod;
                        index++;
                    }
                }
                else
                {
                    result = declaredMethods;
                }
                declaredMethodsCache.put(clazz, (result.length == 0 ? EMPTY_METHOD_ARRAY : result));
            }
            catch (Throwable ex)
            {
                throw new IllegalStateException("Failed to introspect Class [" + clazz.getName() + "] from ClassLoader [" + clazz.getClassLoader() + "]", ex);
            }
        }
        return result;
    }

    @Nullable
    private static List<Method> findConcreteMethodsOnInterfaces(Class<?> clazz)
    {
        List<Method> result = null;
        for (Class<?> ifc : clazz.getInterfaces())
        {
            for (Method ifcMethod : ifc.getMethods())
            {
                if (!Modifier.isAbstract(ifcMethod.getModifiers()))
                {
                    if (result == null)
                    {
                        result = new ArrayList<>();
                    }
                    result.add(ifcMethod);
                }
            }
        }
        return result;
    }

    /**
     * Determine whether the given method is an "equals" method.
     *
     * @see java.lang.Object#equals(Object)
     */
    public static boolean isEqualsMethod(@Nullable Method method)
    {
        if (method == null || !method.getName().equals("equals"))
        {
            return false;
        }
        Class<?>[] paramTypes = method.getParameterTypes();
        return (paramTypes.length == 1 && paramTypes[0] == Object.class);
    }

    /**
     * Determine whether the given method is a "hashCode" method.
     *
     * @see java.lang.Object#hashCode()
     */
    public static boolean isHashCodeMethod(@Nullable Method method)
    {
        return (method != null && method.getName().equals("hashCode") && method.getParameterCount() == 0);
    }

    /**
     * Determine whether the given method is a "toString" method.
     *
     * @see java.lang.Object#toString()
     */
    public static boolean isToStringMethod(@Nullable Method method)
    {
        return (method != null && method.getName().equals("toString") && method.getParameterCount() == 0);
    }

    /**
     * Determine whether the given method is originally declared by {@link java.lang.Object}.
     */
    public static boolean isObjectMethod(@Nullable Method method)
    {
        return (method != null && (method.getDeclaringClass() == Object.class || isEqualsMethod(method) || isHashCodeMethod(method) || isToStringMethod(
                method)));
    }

    /**
     * Determine whether the given method is a CGLIB 'renamed' method,
     * following the pattern "CGLIB$methodName$0".
     *
     * @param renamedMethod the method to check
     */
    public static boolean isCglibRenamedMethod(Method renamedMethod)
    {
        String name = renamedMethod.getName();
        if (name.startsWith(CGLIB_RENAMED_METHOD_PREFIX))
        {
            int i = name.length() - 1;
            while (i >= 0 && Character.isDigit(name.charAt(i)))
            {
                i--;
            }
            return (i > CGLIB_RENAMED_METHOD_PREFIX.length() && (i < name.length() - 1) && name.charAt(i) == '$');
        }
        return false;
    }

    /**
     * Make the given method accessible, explicitly setting it accessible if
     * necessary. The {@code setAccessible(true)} method is only called
     * when actually necessary, to avoid unnecessary conflicts with a JVM
     * SecurityManager (if active).
     *
     * @param method the method to make accessible
     * @see java.lang.reflect.Method#setAccessible
     */
    @SuppressWarnings("deprecation")  // on JDK 9
    public static void makeAccessible(Method method)
    {
        if ((!Modifier.isPublic(method.getModifiers()) || !Modifier.isPublic(method.getDeclaringClass().getModifiers())) && !method.isAccessible())
        {
            method.setAccessible(true);
        }
    }


    // Field handling

    /**
     * Attempt to find a {@link Field field} on the supplied {@link Class} with the
     * supplied {@code name}. Searches all superclasses up to {@link Object}.
     *
     * @param clazz the class to introspect
     * @param name  the name of the field
     * @return the corresponding Field object, or {@code null} if not found
     */
    @Nullable
    public static Field findField(Class<?> clazz, String name)
    {
        return findField(clazz, name, null);
    }

    /**
     * Attempt to find a {@link Field field} on the supplied {@link Class} with the
     * supplied {@code name} and/or {@link Class type}. Searches all superclasses
     * up to {@link Object}.
     *
     * @param clazz the class to introspect
     * @param name  the name of the field (may be {@code null} if type is specified)
     * @param type  the type of the field (may be {@code null} if name is specified)
     * @return the corresponding Field object, or {@code null} if not found
     */
    @Nullable
    public static Field findField(Class<?> clazz, @Nullable String name, @Nullable Class<?> type)
    {
        Assert.notNull(clazz, "Class must not be null");
        Assert.isTrue(name != null || type != null, "Either name or type of the field must be specified");
        Class<?> searchType = clazz;
        while (Object.class != searchType && searchType != null)
        {
            Field[] fields = getDeclaredFields(searchType);
            for (Field field : fields)
            {
                if ((name == null || name.equals(field.getName())) && (type == null || type.equals(field.getType())))
                {
                    return field;
                }
            }
            searchType = searchType.getSuperclass();
        }
        return null;
    }

    /**
     * Set the field represented by the supplied {@link Field field object} on the
     * specified {@link Object target object} to the specified {@code value}.
     * In accordance with {@link Field#set(Object, Object)} semantics, the new value
     * is automatically unwrapped if the underlying field has a primitive type.
     * <p>Thrown exceptions are handled via a call to {@link #handleReflectionException(Exception)}.
     *
     * @param field  the field to set
     * @param target the target object on which to set the field
     * @param value  the value to set (may be {@code null})
     */
    public static void setField(Field field, @Nullable Object target, @Nullable Object value)
    {
        try
        {
            field.set(target, value);
        }
        catch (IllegalAccessException ex)
        {
            handleReflectionException(ex);
            throw new IllegalStateException("Unexpected reflection exception - " + ex.getClass().getName() + ": " + ex.getMessage());
        }
    }

    /**
     * Get the field represented by the supplied {@link Field field object} on the
     * specified {@link Object target object}. In accordance with {@link Field#get(Object)}
     * semantics, the returned value is automatically wrapped if the underlying field
     * has a primitive type.
     * <p>Thrown exceptions are handled via a call to {@link #handleReflectionException(Exception)}.
     *
     * @param field  the field to get
     * @param target the target object from which to get the field
     * @return the field's current value
     */
    @Nullable
    public static Object getField(Field field, @Nullable Object target)
    {
        try
        {
            return field.get(target);
        }
        catch (IllegalAccessException ex)
        {
            handleReflectionException(ex);
            throw new IllegalStateException("Unexpected reflection exception - " + ex.getClass().getName() + ": " + ex.getMessage());
        }
    }

    /**
     * Invoke the given callback on all locally declared fields in the given class.
     *
     * @param clazz the target class to analyze
     * @param fc    the callback to invoke for each field
     * @throws IllegalStateException if introspection fails
     * @see #doWithFields
     * @since 4.2
     */
    public static void doWithLocalFields(Class<?> clazz, FieldCallback fc)
    {
        for (Field field : getDeclaredFields(clazz))
        {
            try
            {
                fc.doWith(field);
            }
            catch (IllegalAccessException ex)
            {
                throw new IllegalStateException("Not allowed to access field '" + field.getName() + "': " + ex);
            }
        }
    }

    /**
     * Invoke the given callback on all fields in the target class, going up the
     * class hierarchy to get all declared fields.
     *
     * @param clazz the target class to analyze
     * @param fc    the callback to invoke for each field
     * @throws IllegalStateException if introspection fails
     */
    public static void doWithFields(Class<?> clazz, FieldCallback fc)
    {
        doWithFields(clazz, fc, null);
    }

    /**
     * Invoke the given callback on all fields in the target class, going up the
     * class hierarchy to get all declared fields.
     *
     * @param clazz the target class to analyze
     * @param fc    the callback to invoke for each field
     * @param ff    the filter that determines the fields to apply the callback to
     * @throws IllegalStateException if introspection fails
     */
    public static void doWithFields(Class<?> clazz, FieldCallback fc, @Nullable FieldFilter ff)
    {
        // Keep backing up the inheritance hierarchy.
        Class<?> targetClass = clazz;
        do
        {
            Field[] fields = getDeclaredFields(targetClass);
            for (Field field : fields)
            {
                if (ff != null && !ff.matches(field))
                {
                    continue;
                }
                try
                {
                    fc.doWith(field);
                }
                catch (IllegalAccessException ex)
                {
                    throw new IllegalStateException("Not allowed to access field '" + field.getName() + "': " + ex);
                }
            }
            targetClass = targetClass.getSuperclass();
        } while (targetClass != null && targetClass != Object.class);
    }

    /**
     * This variant retrieves {@link Class#getDeclaredFields()} from a local cache
     * in order to avoid the JVM's SecurityManager check and defensive array copying.
     *
     * @param clazz the class to introspect
     * @return the cached array of fields
     * @throws IllegalStateException if introspection fails
     * @see Class#getDeclaredFields()
     */
    private static Field[] getDeclaredFields(Class<?> clazz)
    {
        Assert.notNull(clazz, "Class must not be null");
        Field[] result = declaredFieldsCache.get(clazz);
        if (result == null)
        {
            try
            {
                result = clazz.getDeclaredFields();
                declaredFieldsCache.put(clazz, (result.length == 0 ? EMPTY_FIELD_ARRAY : result));
            }
            catch (Throwable ex)
            {
                throw new IllegalStateException("Failed to introspect Class [" + clazz.getName() + "] from ClassLoader [" + clazz.getClassLoader() + "]", ex);
            }
        }
        return result;
    }

    /**
     * Given the source object and the destination, which must be the same class
     * or a subclass, copy all fields, including inherited fields. Designed to
     * work on objects with public no-arg constructors.
     *
     * @throws IllegalStateException if introspection fails
     */
    public static void shallowCopyFieldState(final Object src, final Object dest)
    {
        Assert.notNull(src, "Source for field copy cannot be null");
        Assert.notNull(dest, "Destination for field copy cannot be null");
        if (!src.getClass().isAssignableFrom(dest.getClass()))
        {
            throw new IllegalArgumentException(
                    "Destination class [" + dest.getClass().getName() + "] must be same or subclass as source class [" + src.getClass().getName() + "]");
        }
        doWithFields(src.getClass(), field -> {
            makeAccessible(field);
            Object srcValue = field.get(src);
            field.set(dest, srcValue);
        }, COPYABLE_FIELDS);
    }

    /**
     * Determine whether the given field is a "public static final" constant.
     *
     * @param field the field to check
     */
    public static boolean isPublicStaticFinal(Field field)
    {
        int modifiers = field.getModifiers();
        return (Modifier.isPublic(modifiers) && Modifier.isStatic(modifiers) && Modifier.isFinal(modifiers));
    }

    /**
     * Make the given field accessible, explicitly setting it accessible if
     * necessary. The {@code setAccessible(true)} method is only called
     * when actually necessary, to avoid unnecessary conflicts with a JVM
     * SecurityManager (if active).
     *
     * @param field the field to make accessible
     * @see java.lang.reflect.Field#setAccessible
     */
    @SuppressWarnings("deprecation")  // on JDK 9
    public static void makeAccessible(Field field)
    {
        if ((!Modifier.isPublic(field.getModifiers()) || !Modifier.isPublic(field.getDeclaringClass().getModifiers()) || Modifier.isFinal(
                field.getModifiers())) && !field.isAccessible())
        {
            field.setAccessible(true);
        }
    }


    // Cache handling

    /**
     * Clear the internal method/field cache.
     *
     * @since 4.2.4
     */
    public static void clearCache()
    {
        declaredMethodsCache.clear();
        declaredFieldsCache.clear();
    }


    /**
     * Action to take on each method.
     */
    @FunctionalInterface
    public interface MethodCallback
    {

        /**
         * Perform an operation using the given method.
         *
         * @param method the method to operate on
         */
        void doWith(Method method) throws IllegalArgumentException, IllegalAccessException;
    }


    /**
     * Callback optionally used to filter methods to be operated on by a method callback.
     */
    @FunctionalInterface
    public interface MethodFilter
    {

        /**
         * Determine whether the given method matches.
         *
         * @param method the method to check
         */
        boolean matches(Method method);
    }


    /**
     * Callback interface invoked on each field in the hierarchy.
     */
    @FunctionalInterface
    public interface FieldCallback
    {

        /**
         * Perform an operation using the given field.
         *
         * @param field the field to operate on
         */
        void doWith(Field field) throws IllegalArgumentException, IllegalAccessException;
    }


    /**
     * Callback optionally used to filter fields to be operated on by a field callback.
     */
    @FunctionalInterface
    public interface FieldFilter
    {

        /**
         * Determine whether the given field matches.
         *
         * @param field the field to check
         */
        boolean matches(Field field);
    }

}
